I had the same kind of growth on my clowns side. Appeared to be a wound from a scrape. Lured him to the top, netted him,layer him on a wet towel,wiped the excess off with a Qtip and dabbed the wound with iodine on the other side of the Qtip. Wound healed and growth never reappeared. Got the idea from another reefer and it really workers well. Much less stressfull than quarantining for treatment.